This invention relates to a downhole tool, and in particular to a casing or liner shoe.
In oil and gas exploration and production operations, bores are drilled to gain access to subsurface hydrocarbon-bearing formations. The bores are typically lined with steel tubing, known as tubing, casing and liner, depending upon diameter, location and function. Bores may also be lined with a filtration medium, such as slotted pipe or tube, or filtration media comprising a combination of two or more of slotted pipe or tubing, slotted screens or membranes and sand-filled screens. Embodiments of the present invention may be useful in some or all of these applications, and for brevity reference will generally made to xe2x80x9ctubingxe2x80x9d. The tubing is run into the drilled bore from the surface and suspended or secured in the bore by appropriate means, such as a casing or liner hanger. For casing, cement may then be introduced into the annulus between the tubing and the bore wall.
As the tubing is run into the bore the tubing end will encounter irregularities and restrictions in the bore wall, for example ledges formed where the bore passes between different formations and areas where the bore diameter decreases due to swelling of the surrounding formation. Further, debris may collect in the bore, particularly in highly deviated or horizontal bores. Accordingly, the tubing end may be subject to wear and damage as the tubing is lowered into the bore.
These difficulties may be alleviated by providing a xe2x80x9cshoexe2x80x9d on the tubing end. Proposals for casing shoes of various forms are described in Canadian Patent No. 1,222,448, U.S. Pat. Nos. 2,334,788 and 4,825,947 and International Patent Application WO96 28635.
It is among the objectives of embodiments of the present invention to provide an improved tubing shoe.
According to the present invention there is provided a tubing shoe comprising a body for mounting on the lower end of rotatable tubing, and a rigid reaming portion comprising reaming members extending helically around the body towards the leading end thereof in an opposite direction to the intended direction of rotation of the tubing.
According to another aspect of the present invention there is provided a method of reaming a bore in preparation for receiving tubing, the method comprising the steps of:
mounting a tubing shoe on the lower end of tubing, the tubing shoe comprising a body and reaming members extending helically around the body towards the leading end thereof in one direction; and
running the tubing into a bore while rotating the tubing in the opposite direction to said one direction.
In use, these aspects of the present invention facilitate running in of tubing such as casing or liner which is supported or mounted such that it may be rotated as it is run into a bore: liner is typically run in on drill pipe, which may be rotated from surface as necessary; casing may be rotated using a top drive. In the interest of brevity, reference will be made herein primarily to liner. By providing reaming members which extend helically around the body in the opposite direction to the rotation of the liner, the reaming members do not tend to xe2x80x9cbitexe2x80x9d into obstructions in the bore wall; in conventional shoes provided with helical blades or flutes which extend in the same direction as the rotation of the liner the blades tend to engage obstructions, in a similar manner to a screw. In contrast, in the present invention, the members will tend to ride on or over any obstruction as the members ream the bore to the desired diameter to allow the liner to pass. This minimises the possibility of the shoe and liner becoming stuck fast in the bore due to the shoe becoming locked with a bore obstruction.
While the body and reaming portion are preferably substantially cylindrical, the leading end of each reaming member may define a pilot reaming portion defining a smaller diameter than a subsequent reaming portion. Most preferably, the reaming portions include a cutting or rasping surface or inserts on an outer surface of the portions, such as blocks or inserts of tungsten carbide, diamond or other hard material welded or otherwise fixed to the body or reaming members. The pilot and subsequent reaming portions of each reaming member may be helically aligned, or may be staggered. In a preferred embodiment, the reaming members are provided with inserts of hard material, such as tungsten carbide; testing has shown that such inserts provide more effective cutting and members provided with such inserts are harder wearing. It is believed that the ability to press the inserts into interference fit holes or slots avoids the stresses and other material property changes induced by welding blocks of tungsten carbide in place, and the inserts are spaced apart on the reaming members and are effectively self-cleaning, unlike traditional welded tungsten carbide blocks which require cleaning and often become xe2x80x9ccloggedxe2x80x9d.
Each reaming member may include a stabilising portion, which may extend rearwardly of a reaming portion. Most preferably, the stabilising portion has a relatively smooth and hard wearing outer surface, for example of machined tungsten carbide. Alternatively, or in addition, a torque reducing sleeve or centraliser may be provided on the body rearwardly of the reaming portion. Preferably, the centraliser is spaced rearwardly of the reaming portion. Most preferably, the centraliser is rotatable relative to the body. In the preferred embodiment, the centraliser defines a bushing or sleeve, and one or more fluid conduits may carry fluid to provide lubrication between the bushing and the shoe body. In other embodiments the fluid conduits may be omitted. The centraliser may define raised helical flutes or blades. Preferably, the blades extend in the same direction as the intended direction of rotation of the shoe, that is in the opposite direction to the reaming members. In other embodiments the centraliser blades may extend in the same direction as the reaming members. The centraliser blades may include one or both of axial lead in and lead out portions, the portions facilitating relative axial movement of the centraliser relative to the bore wall. In other embodiments, the centraliser blades may be xe2x80x9cstraightxe2x80x9d, that is extend solely axially.
Alternatively, or in addition, further torque reducing sleeves or centralisers may be provided rearwardly of the shoe or on the liner itself.
The trailing edge of each reaming member may define a back reaming portion, which back reaming portions may include a cutting or rasping surface, such as blocks or inserts of tungsten carbide or other hard material welded, located in bores, or otherwise fixed to the body. This feature is useful in shoes having a reduced diameter portion in which material may gather or become trapped, hindering retraction or withdrawal of the shoe. In the preferred embodiment of the invention there is little or no reduction in shoe body diameter following the reaming members, such that it is not necessary to provide the back reaming feature. Most conveniently, the shoe tapers towards the leading end thereof.
The body may define a fluid transmitting conduit in communication with fluid outlets located between the reaming members; due to the orientation of the members, the rotation of the shoe will not tend to clear cuttings and other material from the channels or flutes between the members, and passing fluid into the channels facilitates maintaining the channels clear of cuttings and the like. Most preferably, the fluid outlets are arranged to direct fluid rearwardly of the leading end of the shoe. Conveniently, at least adjacent fluid outlets are longitudinally offset, to minimise weakening of the shoe body. In other embodiments, such fluid outlets may be provided on a nose portion on the body, the outlets being arranged to direct fluid rearwardly towards or between the reaming members.
Preferably also, the body includes a nose portion, preferably an eccentric nose portion, that is the leading end of the nose portion is offset from the shoe axis. Most preferably, the nose portion is of a relatively soft material, for example an aluminium or zinc alloy, or indeed any suitable material, to allow the nose to be drilled out once the liner has been located in a bore. The nose portion may define one or more jetting ports, depending upon the desired flow rate of fluid from the nose portion. One or more jetting ports may be provided toward a leading end of the nose portion; in one preferred embodiment, a jetting port may be provided aligned with the shoe axis. One or more jetting ports may be provided toward a trailing end of the nose portion; in one preferred embodiment a plurality of spaced jetting ports are provided around a base of the nose portion and, in use, direct fluid rearwardly towards the reaming members. The one or more ports provided on the nose portion may open into respective recesses in the nose portion surface, to facilitate in the prevention of the jetting ports becoming blocked or plugged. In the preferred embodiment, the nose portion is rotatable relative to the body, to facilitate passage of the shoe over ledges and the like. Most preferably, the nose is rotatable only to a limited extent, for example through 130xc2x0; this facilitates the drilling or milling out of the nose. Of course, if the nose portion is not required to be drillable, the nose portion may be freely rotatable relative to the body. The nose may be biased towards a particular xe2x80x9ccentredxe2x80x9d orientation by a spring or the like.
According to a further aspect of the present invention there is provided a tubing shoe comprising: a fluid transmitting body for mounting on the lower end of tubing; reaming members on the body; and fluid outlets for directing fluid towards or between the members.
Preferably, the fluid outlets are arranged to direct fluid rearwardly of the leading end of the shoe.
Preferably also, at least adjacent fluid outlets are longitudinally offset.
The fluid outlets may be provided in a nose located on the leading end of the shoe.
According to a still further aspect of the present invention there is provided a method of reaming a bore in preparation for receiving tubing, the method comprising the steps of:
mounting a tubing shoe on the lower end of tubing, the tubing shoe comprising a fluid transmitting body, reaming members on the body, and fluid outlets for directing fluid towards or between the members;
running the tubing into a bore; and
passing fluid through said outlets.
According to another aspect of the present invention there is provided a tubing shoe comprising a body for mounting on the lower end of tubing, and reaming members on the body, the leading end of each reaming member defining a pilot reaming portion defining a smaller diameter than a subsequent reaming portion.
Preferably, the reaming members each define a cutting or rasping surface, such as blocks or inserts of tungsten carbide or other hard material welded, held in bores or slots or otherwise fixed to the body. Most preferably, the reaming members extend helically around the outer surface of each member. Preferably also, the cutting or rasping surfaces of the reaming members combine to provide substantially complete coverage around the circumference of the body. Thus, even if there is no rotation of the shoe as it is advanced into a bore, there is cutting or rasping capability around the circumference of the bore and the bore is reamed to at least a minimum diameter corresponding to the diameter defined by the cutting or rasping surface.
According to another aspect of the present invention there is provided a tubing shoe comprising: a body for mounting on the end of a tubing string; and reaming members extending longitudinally and helically around the body, the reaming members providing substantially complete circumferential coverage of the body whereby, in use, when the tubing shoe is advanced axially into a bore, the reaming members provide reaming around the shoe circumference.
According to a further aspect of the present invention there is provided a method of clearing a bore to receive tubing, the method comprising:
mounting a tubing shoe on the end of a tubing string, the shoe having reaming members extending longitudinally and helically around the body, the reaming members providing substantially complete circumferential coverage of the body; and
advancing the tubing shoe axially into the bore, the reaming members provide reaming around the shoe circumference.
These aspects of the invention are of particular application in tubing shoes which are not subject to rotation during running in to a bore.
The inclination of the reaming members to the longitudinal axis of the shoe may be constant or may vary over the length of the members, for example the members may include portions parallel of perpendicular to the shoe longitudinal axis.
According to a further aspect of the present invention there is provided a tubing shoe comprising: a body for mounting on the end of a tubing string; and a nose rotatably mounted on the body.
Preferably, the nose is rotatable about a longitudinal axis.
Preferably also, the degree of rotation of the nose relative to the body is restricted, to facilitate drilling or milling through the nose.
According to a still further aspect of the present invention there is provided a tubing shoe comprising: a body for mounting on the end of a tubing string; and a torque reducing sleeve or centraliser on the body.
Preferably, the centraliser is rotatably mounted on the body. Most preferably, the body defines a fluid conduit and a bearing area between the centraliser and the body is in fluid communication with the conduit, to supply lubricating fluid to the bearing area.
Preferably also, the centraliser defines external blades or flutes. The blades may extend helically, and may include one or both of substantially axial lead in and lead out portions. Where the shoe includes reaming members, the centraliser blades may extend in the same or the opposite direction to the reaming members.
According to a yet further aspect of the present invention there is provided a tubing shoe comprising:
a body for mounting on the end of a tubing string; and
a rigid reaming portion comprising reaming members extending helically around the body and comprising inserts of relatively hard material on bearing surfaces of the reaming members.
The various aspects of the invention as described above may be manufactured and assembled by various methods. For example, the body and reaming members may be machined from a single billet. However, it is preferred that the body is formed of a single part on which a sleeve defining the reaming members is mounted. A centralising sleeve may also be provided for mounting on the body. Conveniently, the body defines a reduced diameter portion on which one or more sleeves are mounted. A rotating sleeve, such as a centraliser, may be retained by a locking ring or the like. A fixed sleeve, such as carries the reaming members, may be pinned to the body, and the pin may also serve to retain a nose portion on the body.
The various aspects of the invention as described above may be provided singly or in combination with one or more of the other aspects. Further, if desired the various aspects of the invention may be provided in combination with one or more of the optional or preferred features of the other aspects of the invention.